1. Field of the Invention
This invention pertains to power transmission, and more particularly to apparatus for driving tracked carriages.
2. Description of the Prior Art
Mobile storage systems for storing books, supplies, and files are well known. Such systems provide high density storage, and therefore they save valuable space in offices, schools, and libraries.
Typical mobile storage systems include two or more parallel rails embedded in or attached to a building floor. One or more relatively long and narrow carriages span the rails. The carriages may be as long as thirty feet, and the number and spacing of the rails are chosen to suit the particular carriage length. The carriages are usually supported by a pair of wheels rolling along each of the rails.
The carriages may be designed to move along the rails under manual power. For that purpose, a hand wheel is usually mounted to a carriage end panel. The hand wheel is connected by various drive components to a shaft that in turn is connected with at least one of the carriage wheels. Manually rotating the hand wheel causes the drive wheels to rotate and move the carriage. Electrically powered carriages are also in wide-spread use. With that design, a suitable electric motor is substituted for the manual hand wheel. The motor shaft is mechanically connected through a suitable mechanism to the carriage drive wheels.
It has been a common practice to design mobile carriages such that the drive wheels are located on the two ends of the carriages. That is, the carriages are driven by a wheel supported on each of the two outermost rails, and the center regions of the carriages are supported on the interior rails by non-driving wheels. In some designs, there is a driving wheel on each of the rails. Those designs require multiple locations of the drive wheels, which is undesirably expensive. Further, the prior design requires a long shaft for connecting the drive wheels on the carriage ends. The long shafts are awkward to assemble and service. In addition, the long shafts may undergo torsional wind-up when used with heavy carriages, such that the drive wheels at the carriage end remote from the electric motor or hand wheel do not rotate in synchronization with the drive wheels at the carriage hand wheel or motor end. Consequently, despite flanges on the drive wheels, the carriages can tend to skew as they are driven along the rails.
Thus, a need exists for improved driving mechanisms for mobile storage carriages.